Polydiacetylene gels

ABSTRACT

Polydiacetylene gel compositions, comprised of a polydiacetylene and a gel-forming liquid therefor, are described which undergo a change in color and in physical state to a solution when heated to a predetermined temperature. The gel compositions exhibit hysteresis temperature characteristics which allow the original color change to be maintained and recorded until the solution is cooled below the predetermined temperature. Thus, the gel compositions are useful in temperature-indicating devices for reversibly monitoring a wide range of temperatures. A novel class of polydiacetylene compounds is also described, useful in forming the gel compositions, formed from monomeric diacetylenediol bis(alkoxycarbonylmethylurethanes).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel polymeric gel compositions, useful intemperature-indicating devices, containing a polydiacetylene and agel-forming liquid therefor, and also to a novel class ofpolydiacetylenes, useful in forming the gel compositions, formed frommonomeric diacetylene diol-bis(alkoxycarbonylmethylurethanes).

2. Brief Description of the Prior Art

Two types of clinical thermometers currently on the market utilizeorganic compounds as temperature indicating materials in which a colorchange occurs at a predetermined temperature. Both types of devices arebased on particular phase changes of organic compounds, or mixturesthereof, as the principle underlying the color change.

The first type of device (developed by Bio-Medical Sciences Inc.,Fairfield, N.J.) uses the principle of the melting of organic compounds,in which the melt carries a co-mingled dyestuff through a white orcolorless absorbing material, so as to produce a visual color change.However, the device in general is not reusable and also requires aprotective film between the melting compositions and the dyestuff, andin some cases storage at low temperatures prior to use; factors whichtend to increase the overall manufacturing cost. Various modificationsof the device are described in the following patents assigned toBio-Medical Sciences Inc.: U.S. Pat. Nos. 3,981,683 (1976); 3,665,770(1972); 3,677,088 (1972); 3,704,985 (1972); 3,966,414 (1976); and3,980,581 (1976).

A further device is described in U.S. Pat. No. 4,042,336 (1977),assigned to Bio-Medical Sciences, Inc., in which the temperature historyof a product is visually displayed as a color front on an indicator,initiated by a generated gas, the distance of the front advancementbeing a function of the temperature-time integral.

The second type of device (marketed by Clinitemp, Inc., Indianapolis,Ind.) uses color changes produced by liquid crystal transitions, asviewed through either a polarizing or a colored film. These liquidcrystal devices are reversible and thus reusable but have no hysteresisassociated with the color change. As a result, there is little time torecord the temperature once the device is detached from the skin orremoved, for example, from the mouth.

U.S. Pat. No. 3,479,877 (1968) discloses a temperature indicator devicewherein an indicator substance melts, at a predetermined temperature tobe monitored, and flows along a wick, the distance of flow correspondingto the length of exposure time at that particular temperature. However,although the indicator records a time-temperature history, it is notreusable in subsequent applications.

U.S. Pat. No. 3,465,590 (1969) discloses a thermometer device whichutilizes solid solutions of fatty acids and a dye to reversibly orirreversibly indicate when a particular temperature has been reached.However, the composition employed in the device does not possesshysteresis behavior thus allowing a predetermined temperature to beobserved and recorded. Most importantly, the originaltemperature-indicating composition cannot be regenerated and is thus notreusable in subsequent applications.

SUMMARY OF THE INVENTION

We have unexpectedly found a new class of compositions which are highlysuitable as temperature-indicating compositions. The compositions arepolymeric gels, comprising a solid polydiacetylene and gel-formingliquid therefor, and exhibit hysteresis temperature behavior. They arecapable of reversibly indicating when a predetermined temperature hasbeen reached or exceeded, by undergoing a color change and a change inphysical state, together with the attractive advantage of maintainingthis color change until recording can be achieved. The original colorand physical state of the gel is regenerated by simply cooling thecomposition generally about 10° C. below the predetermined temperature.Thus, the composition combines the attractive advantages of bothirreversible and reversible temperature-indicating compositions into onedevice.

In accordance with this invention there is provided a compositioncomprising a polymeric gel consisting essentially of a solidpolydiacetylene, or mixture thereof, and a gel-forming liquid therefor,said gel being colored and being capable of undergoing transformationupon heating to the dissolution temperature, thereby forming a solutionof said polydiacetylene in said liquid, exhibiting a different colorthan said gel, said solution being capable of reversibly reforming thegel in its original color and physical state upon cooling to thegelation temperature, being lower than said dissolution temperature.

Further provided is a device for reversibly indicating when apredetermined temperature has been reached or exceeded including acontainer, a temperature-indicating material positioned inside of saidcontainer, capable of reversibly undergoing a color change when apredetermined temperature has been reached or exceeded, and a means forobserving said color change; the improvement which comprises providing apolymeric gel of this invention as the temperature-indicating materialwherein the color change, formed at the predetermined temperature,persists until a temperature lower than the predetermined temperature isreached thereby restoring the original color and physical state of thegel.

Also provided is a compound of the formula: R--C.tbd.C--C.tbd.C--R',wherein R and R' are independently of the formula: --(CH₂)_(n)--O--CONH--CH₂ --CO--OA, wherein is an integer value of 1 to 10 and A isC₁ -C₁₀ linear or branched alkyl.

Further provided is a colored composition containing up to 10% by weightof a colored polymer derived from at least one compound as describedabove.

Also provided is a colored composition containing from 10 to 100% byweight of a colored polymer derived from at least one compound asdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE illustrates the hysteresis behavior of typicalpolydiacetylene gel compositions of this invention.

DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS

The subject "gel" composition comprises a polymeric gel compositionconsisting essentially of a solid polydiacetylene and a gel-formingliquid therefor. By the term "polymeric gel" as used herein, is meant acolloidal-type of material in which the dispersed phase, i.e. the solidpolydiacetylene, has combined with the continuous phase, i.e. thegel-forming liquid, to produce a viscous, jelly-like product. As furtherdescribed in "The Condensed Chemical Dictionary", by Gessner G. Hawley,Eighth Edition, 1971, by Van Nostrand-Reinhold, p. 412, "a gel is madeby cooling a solution, whereupon certain kinds of solutes (gelatin) formsubmicroscopic crystalline particle groups which retain much solvent inthe interstices." The polymeric gels of this invention exhibitproperties and appearance which are in accord with the description aboveand are best described as being analogous to the well known "Jello". Thegel compositions of this invention are stable, in the absence ofevaporation of the gel-forming liquid, are transparent or translucent,are colored and when heated to a particular temperature, designatedherein as the "dissolution temperature", undergo a change in color andphysical state. Thus, the gels represent an intermediate physical statebetween a solid and a liquid.

By the term "gel-forming" is meant that the liquid interacts with thesolid polydiacetylene by a variety of attractive forces, e.g., van derWaal's forces, solvent-polymer interactions, solvent cage effects,hydrogen-bonding effects and the like, wherein either the solid polymeror gel-forming liquid are not present as separate entities but arecombined into one identifiable and describable mass. The exact physicalnature and structure of the gel composition has not been fullyelucidated.

The gel compositions are capable of reversibly undergoing transformationfrom the gel state to a solution, upon heating to a particulartemperature, designated as the "dissolution temperature", T_(d) whereina color change occurs together with dissolution of the solid polymer inthe gel-forming liquid. The dissolution temperature is a function of theparticular polydiacetylene, the gel-forming liquid used and theconcentration of the polydiacetylene in the gel-forming liquid. Forexample, poly[4,6-decadiyn-1,10-diolbis(n-butoxycarbonylmethylurethane)], hereinafter referred to as poly3DBCMU, in o-dichlorobenzene (ODCB) at 0.1 and 0.5 weight percentages,exhibits a dissolution temperature at 102.8°-103.7° C. and 105.0°-105.4°C., respectively. Whereas, poly [5,7-dodecadiyn-1,12-diolbis(n-butoxycarbonylmethylurethane)], hereinafter referred to as poly4DBCMU, in 0.5 weight percent o-dichlorobenzene, exhibits a dissolutiontemperature at 65.3°-66.6° C. The color of the transition at thedissolution temperature is also dependent upon the particularpolydiacetylene employed. For example, poly 3DBCMU in ODCB exhibits acolor change of blue to yellow while poly 4DBCMU in ODCB exhibits a redto yellow color transition.

The formed solution reverts back to the original gel state upon coolingto a temperature below the dissolution temperature, designated as the"gelation temperature", T_(s), i.e., that temperature at which the gelreforms and the original color of the gel is restored. Thus, the gelexhibits a hysteresis temperature effect in that the formed solutionmust be cooled to a lower temperature for gel reformation compared tothe temperature of gel dissolution, as illustrated in the FIGURE. Theremarkable attribute of the present gel compositions is the fact thatthis hysteresis behavior is reversible throughout many heating andcooling cycles, thus rendering the compositions extremely useful inreversible thermometertype devices.

The gel compositions possess a temperature differential between thedissolution temperature, T_(d), and gelation temperature, T_(s), fromabout 1° to 100° C. and preferred temperature differentials are at leastabout 10° C.

The gel compositions exhibit dissolution temperatures from about -80° to+200° C. and preferably about -77° C. to +130° C. Particularly ofinterest are gel compositions exhibiting color transition temperaturesat about human body temperature, i.e. 98.2° F., such as a 0.5 weightpercent gel of poly 4DBCMU in a 90:10 by volume mixture of methylethylketone/dimethylformamide.

Preferred gel compositions are blue or red in color and the resultingsolution is yellow in color. These are preferred since the color changefrom blue or red to yellow presents a dramatic visible color changewhich is striking and easily observable.

The concentration of polydiacetylene in the gel composition is about0.001 to 50 weight percent and preferably about 0.1 to 10 weightpercent.

Polydiacetylenes which are useful in forming the gel compositions ofthis invention are generally produced by polymerizing monomericdiacetylenes containing at least one conjugated --C.tbd.C--C.tbd.C--grouping and are listed below.

A preferred class of polydiacetylenes useful in the instant inventionfor forming the gel compositions, which polydiacetylenes are also novelin themselves, also being a subject of this invention arepolydiacetylenes formed by polymerizing diacetylene-diolalkoxycarbonylmethylurethane monomers, also being novel and a subject ofthis invention, of the formula: R--C.tbd.C--C.tbd.C--R', wherein R andR' are independently selected from the group:

    --(CH.sub.2).sub.n --O--CONH--CH.sub.2 --CO--OA,

wherein n is an integer value of 1 to 10 and A is C₁ -C₁₀ linear orbranched alkyl. The diacetylene monomers used to form the polymers ofthis invention are symmetrical or unsymmetrical, with respect to n or A,and preferably symmetrical.

Representative examples include the diacetylenes wherein, forconvenience the symbols R, R', A and n have independently the meaningsshown below in Table I.

                  TABLE I                                                         ______________________________________                                        R               R'                                                            n          A        n            A                                            ______________________________________                                        2          ethyl    2            ethyl                                        2          n-butyl  2            n-butyl                                      3          ethyl    3            ethyl                                        3          n-butyl  3            n-butyl                                      3          isopropyl                                                                              3            ethyl                                        3          n-decyl  3            ethyl                                        3          n-octyl  2            ethyl                                        4          ethyl    4            ethyl                                        4          n-butyl  4            n-butyl                                      4          n-decyl  4            n-butyl                                      ______________________________________                                    

Preferred diacetylenes are those wherein R and R' are identical, n is 3or 4 and A is ethyl or n-butyl. In the list below, these preferredcompounds are identified and the chemical names of polydiacetylenes ofthis invention, obtainable therefrom, are shown below in Table II.

                  TABLE II                                                        ______________________________________                                        n     A         Chemical Name                                                 ______________________________________                                        3     ethyl     Poly[4,6-decadiyn-1,10-diol-bis(ethoxy-                                       carbonylmethylurethane)], poly 3DECMU                         3     n-butyl   Poly[4,6-decadiyn-1,10-diol bis(n-butoxy-                                     carbonylmethylurethane)], poly 3DBCMU                         4     ethyl     Poly[5,7-dodecadiyn-1,12-diol bis(ethoxy-                                     carbonylmethylurethane)], poly 4DECMU                         4     n-butyl   Poly[5,7-dodecadiyn-1,12-diol bis(n-butoxy                                    carbonylmethylurethane)], poly 4DBCMU                         ______________________________________                                    

As a class, the above polydiacetylene diol alkoxycarbonylmethylurethanesare useful in forming the invention gel compositions of this invention.

Further polydiacetylenes useful in forming the gel compositions of thisinvention are polydiacetylenes formed from polymerizing diacetylenemonomers of the formula R--C.tbd.C--C.tbd.C--R, wherein R is selectedfrom the group consisting of --(CH₂)_(n) --O--CONH--B, wherein

(a) n is 2 and B is ethyl, n-butyl or m-chlorophenyl;

(b) n is 3 and B is methyl, ethyl, phenyl or m-tolyl;

(c) n is 4 and B is methyl, ethyl, 2-chloroethyl, ochlorophenyl,p-chlorophenyl, n-butyl or m-methoxyphenyl.

In order to obtain the polydiacetylenes useful in forming the gels ofthe present invention and in particular to obtain these polymers in highyields, it is usually necessary to obtain acetylenic monomers withprecursor crystal phases having suitable molecular packing in the solidstate. Monomer suitable for making the polymer of the invention can beprepared by known methods as described in U.S. Pat. No. 3,999,946,supra. For example, the bisalkoxycarbonylmethylurethane derivative canbe prepared by reacting the corresponding diyn-ol or diyn-diol with asuitable isocyanate. Thus, 5,7-dodecadiyn-1,12-diolbis(n-butoxycarbonylmethylurethane was prepared by reacting5,7-dodecadiyn-1,12-diol with n-butyl isocyanatoacetate. A catalyst maybe added to the reaction mixture to increase the reaction rate toproduce the desired acetylenic monomer. Conventional tin catalysts(e.g., dibutyl tin-di-2-ethylhexoate), DBTE, and tertiary amines (e.g.triethyl amine, TEA) have been used as catalysts. The reaction mixturemay also be warmed as for example, to about 45° to 55° C. to speed upthe reaction. Such heating, however, is not required. The desireddiyn-ol or diyn-diol can also be prepared by conventional methods. Thus,for example, 5,7 -dodecadiyn-1,12-diol has been prepared by theoxidative coupling of the corresponding alkylol, i.e. 5-hexyn-1-ol.

The desired monomer, is generally recrystallized from an appropriatesolvent, so as to provide a solid monomer, preferably in a substantiallycrystalline phase, which is polymerizable. Suitable solvents employed inthe solution recrystallization include alkyl esters of monocarboxylicacids, alkyl alcohols, paraffins, olefins, benzenes, alkylated benzenes,ethers, ketones, petroleum ether, halogenated hydrocarbons and water.Representative examples include ethyl acetate, methyl propionate,methanol, ethanol, butanol, isopropanol, hexane, heptane,1,4-dimethylheptane, toluene, xylene, trimethylbenzene, ethyl ether,isopropyl ether, 1,2-dimethoxyethane, tetrahydrofuran, dioxane, acetone,ethylmethyl ketone, chloroform, dichloromethane and trichloromethane andmixtures thereof. Especially preferred as crystallizing solvents are1,2-dimethoxyethane, dioxane, tetrahydrofuran, petroleum ether, acetone,chloroform, benzene, methanol, ethanol, xylene, ethyl acetate, isopropylether and water. Crystallization may, for example be affected by roomtemperature evaporation of solutions containing from 0.01 to 50 partsand preferably about 0.1 to 5 parts by weight of monomer per part ofsolvent volume. Alternately, other conventional crystallizationprocedures may be used such as sublimation or by cooling a saturatedsolution to a sufficiently low temperature (usually at or above roomtemperature that the required crystallization occurs).

The subject polydiacetylenes disclosed herein are produced byirradiating the corresponding diacetylene diolalkoxycarbonylmethylurethane monomer with at least about 0.1 Mrads ofgamma radiation at room temperature or its equivalent at othertemperatures and extracting out unpolymerized monomer from theirradiated polydiacetylene.

The term "0.1 Mrads of gamma radiation at room temperature or itsequivalent at other temperatures" indicates that the dosage of gammaradiation required for polymerization will vary with the temperature atwhich the irradiation is conducted. Higher temperatures will in generalrequire lesser amounts of gamma radiation in conversely lowertemperatures, i.e. below room temperature will generally requireslightly larger amounts of gamma radiation. It is preferred to use adosage of gamma radiation in the range of about 15 to 100 Mrads, buthigher dosages can also be used to insure complete polymerization.

Extraction of the monomer from the irradiated sample can be accomplishedby the use of organic solvents including dialkyl ethers, alcohols andketones. Representative examples are diethylether, diisopropylether(isopropyl ether) methanol, ethanol, acetone and methylethyl ketonewherein acetone and isopropyl ether are preferred.

The infrared spectra of the polydiacetylenes are essentially identicalto those of the monomers, indicating that the polymers possess the samefunctionality as the monomers. Raman spectral evidence indicates that1,4-addition reaction has occurred at the --C.tbd.C--C.tbd.C-- groupwithin the monomer molecule. The Raman intense vibration, at about 2260cm⁻¹ which is characteristic of the conjugated diacetylene functionalityof the pure monomer disappears and is replaced by a characteristic Ramanintense vibration between 1450 and 1540 cm⁻¹ and between 2060 and 2140cm⁻¹ in the polymer. However, if the monomer contains only a fraction ofa percent of polymer, the peak at 2260 cm⁻¹ becomes obscured in themonomer due to the very strong peak at 2140 cm⁻¹ attributable to thepolymer. This was the case found for the monomers in Examples 1-4herein. X-ray diffraction data indicate that the repeat dimension in thechain direction is approximately 4.9 Å or a multiple thereof, withconfirmed spectral evidence that the polymerization has proceded by a1,4-addition reaction.

The term "gel-forming liquids" includes those liquid solvents which actas gel-forming agents for the polydiacetylene below the dissolutiontemperature, T_(d), and act as a solvent for the polydiacetylene abovethis temperature. The gel-forming liquid must be capable of dissolvingat least about one tenth of a gram of polydiacetylene in 100 ml of saidliquid at the dissolution temperature, and more preferably one gram ofpolydiacetylene in 100 ml. of gel-forming liquid at the dissolutiontemperature. The term "gel-forming liquid" is also meant to includemixtures of two or more liquids whose combined properties possess thecharacteristics described above.

Representative examples of gel-forming liquids useful in forming thegels of the instant invention include linear or branched C₅ -C₁₀paraffinic hydrocarbons, linear or branched C₁ -C₅ halogenated alkanes,containing 1-4 halogens, C₂ -C₄ linear or branched alkyl sulfoxides, C₂-C₇ N,N-dialkyl alkanoamides, C₆ -C₁₀ aromatic hydrocarbons, C₆ -C₁₀halogenated aromatic hydrocarbons containing 1 to 4 halogens, C₄ -C₉linear or cyclic mono- or diethers, C₄ -C₆ cyclic sulfones, C₂ -C₄alkanoic acids, C₃ -C₆ linear alkyl ketones, C₂ -C₄ halogenated alkanoicacids, containing 1 to 3 halogens, or mixtures thereof. Aqueoussolutions of the above liquids are also included in the presentinvention.

Specific examples of gel-forming liquids include hexane, methylenedichloride, chloroform, dimethylsulfoxide, tetramethylene sulfone,dimethylformamide, dimethylacetamide, benzene, toluene, xylene,naphthalene, o-dichlorobenzene, trichlorobenzene, diethylether,tetrahydrofuran, dioxane, glyme, acetic acid, propionic acid,trichloroacetic acid, trifluoroacetic acid, water, methylethyl ketone,aqueous solutions thereof, wherein said liquid is water soluble, ormixtures thereof.

Methods of preparation of the gel composition include heating a mixtureof solid polydiacetylene and gel-forming liquid therefor until solutionis achieved, at the dissolution temperature, and then allowing thesolution to cool below the gelation temperature. The heating step ispreferably carried out where substantially no evaporation of thegel-forming liquid occurs.

The gel compositions of this invention are useful in devices forreversibly indicating when a predetermined temperature has been reachedor exceeded. These thermometer-type devices usually comprise acontainer, a temperature-indicating material, positioned inside of thecontainer, capable of visually undergoing a color change when apredetermined temperature has been reached or exceeded, and a means forobserving said color change. The improved device of this inventioncontains the subject gel composition as the temperature-indicatingmaterial. The gel composition is chosen such that the color transitiontemperature is in the same range as the predetermined temperaturedesired to be indicated. When the predetermined temperature is reached,the gel composition forms a solution and undergoes a color change, andthis color change persists, allowing the temperature to be observed andrecorded, until the temperature is lowered below the dissolutiontemperature to the gelation temperature thereby restoring the originalcolor and physical state of the gel.

The nature of the container, positioning of the temperature-indicatingmaterial inside said container, and means for observing the color changeof the temperature-indicator are well known in the art as, exemplifiedby the above-described patents assigned to Bio-Medical Sciences, Inc.,which are hereby incorporated by reference. Further elucidation of thenature of the elements is deemed unnecessary as being obvious to oneskilled in the art.

The device is constructed by placing a polydiacetylene gel compositionof this invention in a suitable container wherein the polydiacetylene ischosen to have a dissolution temperature in the range to be monitored.For example, if it is desired to monitor abnormally high human bodytemperature, as is present during a fever, a 0.5 weight percent gelcomposition of poly 4-DBCMU, in 90-10 percentage by volume ofmethylethyl ketone/DMF, may be employed. The container can be of anymaterial that is chemically inert to the gel composition, is not solubletherein, and is tightly sealed to prevent evaporation of the gel-formingliquid agent during the temperature-indicating process. Suitablecontainer materials are glass, transparent and solvent-impermeableplastics.

The gel composition in the device is positioned such that the resultingcolor change is readily observable upon reaching or exceeding thedesired predetermined temperature.

Given the polydiacetylene gel composition, disclosed herein, one skilledin the art will readily be able to construct various modifications oftemperature-indicating devices and thermometers. Such devicesincorporating gel compositions of this invention, as the temperatureindicating device, will be obvious to one skilled in the art.

Also a subject of this invention is a partially polymerized coloredcomposition containing up to 10% by weight of a colored polymer derivedfrom polymerizing at least one diacetylene diolalkoxycarbonylmethylurethane monomer as described above.

The polymerization can be conducted by thermal annealing or irradiatingthe corresponding diacetylene diol alkoxycarbonylmethylurethane monomer,of the formula described above, with ultraviolet radiation or gammaradiation up to a dosage of about 5 Mrads at room temperature or itsequivalent at other temperatures. Dosages larger than 5 Mrads aregenerally required at temperatures below room temperature, and viceversa since the required dosage of gamma radiation will vary in generalwith the temperature at which the radiation is conducted.

Ultraviolet radiation of short or long wave lengths can be employed toproduce the partially polymerized polydiacetylenes and short wave lengthultraviolet radiation is preferred. Usually, radiation times of a fewsecond to several hours are sufficient to produce the partiallypolymerized polyacetylene with a conventional lamp having an intensityof 6250 microwatts at a distance of 15 inches from the source or itsequivalent. Thermal annealing can also be employed to produce thepartially polymerized polydiacetylene and usually a temperature fromabout 20° to 80° C. is used and preferably 20° to 30° C. for a period ofone day to 6 months is utilized.

The partially polymerized compositions are useful in producing the fullypolymerized compositions described herein, and in some cases are usefulas "thermochromic" materials in temperature-indicating devices, whereinthe term "thermochromic" and the devices are described in U.S.application Ser. No. 839,678, hereby incorporated by reference. Forexample, partially polymerized [5,7-dodecadiyn-1,12-diolbis(n-butoxycarbonylmethylurethane)] prepared by thermal annealing atroom temperature for one month, containing about 1.5 weight percent ofpolymer, exhibits a thermochromic transition temperature at about 40° C.and changes from a blue to violet in color. Likewise, partiallypolymerized [5,7-dodecadiyn-1,12-diol bis(ethoxycarbonylmethylurethane)]prepared in the same manner as above, exhibits similar physicalproperties. Use of the above partially polymerized materials intemperature-indicating or indicia-display devices will be obvious inlight of the disclosure of the above-identified U.S. application, herebyincorporated by reference.

A colored composition containing from 10 to 100% by weight of a coloredpolymer derived by polymerizing at least one diacetylene diolalkoxycarbonylmethylurethane monomer composition, defined hereinabove,is also subject of this invention. These polymeric compositions find useas thermochromic color-indicating solids in temperature-indicating andindicia-display devices described in U.S. application Ser. No. 839,678,hereby incorporated by reference.

As a class, the fully polymeric diacetylene diolalkoxycarbonylmethylurethanes are thermochromic and preparation and usethereof in the above-mentioned devices will be obvious to one skilled inthe art from this disclosure and the above-identified reference.

The term "fully polymeric" as used herein refers to thosepolydiacetylenes which have been monomer-extracted as being preferredembodiments in the applications described herein. However,polydiacetylenes containing from 10 to 100 weight percent polymer, arealso useful in the stated applications and can also be used to producethe fully polymeric composition by a monomer-extraction process.

The fully polymeric compositions are also useful in producing shapedarticles therefrom such as films and fibers, being also a subject ofthis invention. For example, poly 4DBCMU can be molded into a film at aprocessing temperature of about 150° C. The resulting film isthermochromic and can be used in temperature-indicating andindicia-display devices. The processing steps for producing film andfibers from the polymeric composition are conventional and known in theart. In addition, the fully polymerized compositions can be incorporatedinto other polymers, for example, Halar™, a chlorotrifluoroethylenecopolymer, produced by Alied Chemical Corporation (USA), to produceuseful temperature-indicating or indicia-display devices. For example,poly 4DBCMU can be incorporated into Halar film by milling a mixture ofthe two materials at 500° C., said mixture containing about 5 percent byweight of the polydiacetylene. The resulting light orange-colored filmis thermochromic at 110° C. wherein it turns to a red color. The shapedfilm is useful as a device in temperature-indicating and indicia-displayapplications, and similarly, fibers containing the subjectpolydiacetylenes of this invention are also useful intemperature-indicating and indicia-display applications.

The compositions containing 100% by weight fully polymerized material,being monomer-extracted by a suitable solvent such as acetone orisopropyl ether, are useful in the gel compositions of this invention,as described hereinabove.

The following examples are illustrative of the best mode of carrying outthe invention as contemplated by us and should not be construed as beinglimitations on the scope or spirit of the invention.

EXAMPLE 1 Synthesis of 4,6-decadiyn-1,10-diolbis(ethoxycarbonylmethylurethane); 3DECMU Synthesis:

To a 1000 ml 3-necked flask fitted with a magnetic stirrer, an additionfunnel and a thermometer, 16.6 grams (0.1 mole) of4,6-decadiyn-1,10-diol in 400 ml of tetrahydrofuran was added. 1 g ofdi-t-butyl-tin-di-2-hexoate and 2 ml of triethylamine were added ascatalysts. The resulting solution was stirred and 32.5 g of ethylisocyanatoacetate,

    (C.sub.2 H.sub.5 --O--CO--CH.sub.2 --N═C═O),

was added dropwise over a period of half an hour. The reactiontemperature, 25° C., was kept constant by a cold water bath. Thereaction was allowed to proceed for 2 hours and then poured into 3000 mlof hexane. The resulting precipitate was collected by filtration anddried under vacuum. The product weighed 42 grams (yield=98.1%), m.p.82.6°-83.7° C. Results of elemental analysis and main absorption peaksobserved in the infrared spectrum are listed below.

Elemental Analysis: Calculated: C=56.60; H=6.60; N=6.60, O=30.19, Found:C=56.58; H=6.47; N=6.30; O=30.42

Infrared Spectrum: (1) urethane group: 3340 cm⁻¹ (NH Stretching), 1690cm⁻¹ (COO) 1550 cm⁻¹ (NH,CN), 1300 cm⁻¹ (CN,NH); (2) ester group: 1750cm⁻¹ (COO), 1212 cm⁻¹ (C--O--C); (3) CH₂ --O group: 1361 cm⁻¹, 1472 cm⁻¹(CH₂ -O ester)

Solid State Polymerization

The title compound turned blue at room temperature within 24 hrs.indicating thermal solid state polymerizability. Irradiation of theabove compound by Co⁶⁰ gamma rays at a dosage of 50 Mrads at roomtemperature resulted in a metallic (green-gold) polymer. The resultingmaterial was treated with boiling acetone in a Soxhlet extractor for 3hours to remove unreacted monomer. Obtained were 0.9 g polymer, meltingpoint 195° C., indicating a 90% polymer conversion. Results of theelemental analysis and main absorption bands observed in the infraredspectrum and Raman spectrum are listed below.

Elemental Analysis: Calculated: C=56.03; H=6.60; N=6.60; O=30.18; Found:C=56.04; H=6.62; N=6.42; O=31.81

Infrared Spectrum: (1) urethane group: 3340 cm⁻¹ (N--H stretching), 1698(COO); 1543 cm⁻¹ (NH,CN), 1196 cm⁻¹ (CN,NH); (2) ester group: 1752 cm⁻¹(COO), 1196 cm⁻¹ (C--O--C);

Raman Spectrum: 2078 cm⁻¹ (C.tbd.C), 1459 cm⁻¹ (C═C)

Thermochromism:

The metallic green-gold polymer produced above changed to a red (orange)color upon heating to 195° C. On cooling the solid to room temperature,it reverted back to its original metallic green-gold color. Thisthermochromic cycle was repeated many times with no apparentdegradation.

The above polydiacetylene, produced by gamma irradiation, wassuccessfully incorporated into Halar™ (made by Allied ChemicalCorporation), an ethylene-chlorotrifluoroethylene copolymer, first bymilling the two materials at 500° F. and then molding the resulting massat the same temperature. The Halar film, containing 5.0 percent byweight of the polydiacetylene, was black in color, and turned an orangecolor upon heating to 196° C. and reverted back to the black color uponcooling to room temperature.

The above polydiacetylene produced by gamma irradiation was molded at210° C. to yield a film of about 3 mil in thickness. The polydiacetylenefilm changed from a green-gold to orange color upon heating to 196° C.The film was reasonably strong being comparable with polyethylene filmand was pliable.

EXAMPLE 2 Synthesis of 4,6-decadiyn-1,10-diol bis(n-butoxycarbonylmethyl urethane), 3DBCMU. Synthesis:

Following the procedure of Example 1, 8.3 grams (0.05 mole) of4,6-decadiyn-1,10-diol and 19.6 g (0.125 mole) of butylisocyanatoacetate, (CH₃ --(CH₂)₃ --O--CO--CH₂ --N═C═O) were reacted inthe presence of 0.5 g of di-t-butyl-tin-di-2-ethylhexanoate, 1 ml oftriethylamine and 400 ml of tetrahydrofuran. The reaction was allowed tostir for two hours, and was then poured into 3000 ml of hexane. Theresulting precipitate was collected by filtration and dried undervacuum. The product weighed 23.5 g, (98.1% yield), m.p. 65.4°-68° C.Results of elemental and main absorption peaks observed in the infraredspectrum are listed below.

Analytical: Elemental Analysis: Calculated: C=60.00; H=7.50; N=5.83;O=26.66; Found: C=59.72; H=7.57; N=5.53; O=26.85

Infrared Spectrum: (1) Urethane group: 3340 cm⁻¹ (NH), 1690 cm⁻¹ (COO),1550 cm⁻¹ (NH, CN), 1298 cm⁻¹ (CN, NH); (2) Ester group: 1740 cm⁻¹(COO), 1212 cm⁻¹ (C--O); (3) --CH₂ --O-- group: 1472 cm⁻¹ and 1378 cm⁻¹(CH₂ --O)

Solid State Polymerization:

The above compound turned blue within 24 hrs. at room temperatureindicating thermal solid state polymerizability.

The above-prepared compound was crystallized from acetone and hexane.The crystallized diacetylene was irradiated with Co⁶⁰ gamma rays at adosage of 50 Mrads at room temperature, producing a metallic(green-gold) polydiacetylene polymer. One gram of the unreacted monomerwas extracted with acetone in a Soxhlet apparatus yielding 0.53 gpolymer, melting point, 183° C. The conversion of monomer to polymer wasthus 53%. Results of elemental analysys and main absorption peaksobserved in the infrared spectrum and Raman spectrum are listed below.

Elemental Analysis: Calculated: C=60.00; H=7.50; N=5.83; O=26.66; Found:C=59.17; H=7.27; N=5.40; O=29.03

Infrared Spectrum: (1) urethane group: 3340 cm⁻¹ (N--H stretching), 1693cm⁻¹ (COO), 1545 cm⁻¹ (NH,CN), 1200 cm⁻¹ (CN,NH); (2) ester group: 1753and 1745 cm⁻¹ (COO), 1200 cm⁻¹ (C--O--C)

Raman Spectrum: 2084 cm⁻¹ (C.tbd.C), 1458 cm⁻¹ (C═C)

Thermochromism:

The metallic green-gold polymer produced above changed to a red (orange)color upon heating to 185° C. On cooling the solid to room temperature,it reverted back to its original metallic green gold color. Thisthermochromic cycle was repeated many times without any apparentdegradation.

The above polydiacetylene produced by gamma irradiation was molded at200° C. into a thin green-gold colored (about 3 mil) film. Upon heatingto 185° C., the film turned red (orange) in color. On cooling to roomtemperature, it reverted back to a metallic green gold color. The filmwas reasonably strong (being comparable to polyethylene) and waspliable.

EXAMPLE 3 Synthesis of 5,7-dodecadiyn-1,12-diol bis(ethoxycarbonylmethyl-urethane), 4DECMU. Synthesis:

Following the general procedure of Example 1, 9.7 g (0.05 mole)5,7-dodecadiyn-1,12-diol and 16.0 grams of ethyl isocyanatoacetate, (C₂H₅ --O--CO--CH₂ --N═C═O), were reacted in the presence of 0.5 g ofdi-t-butyl-tin-di-2-ethylhexoate, 1 ml of triethylamine and 200 ml oftetrahydrofuran. The reaction was allowed to proceed for two hours, andwas then poured into 2000 ml of hexane. The resulting precipitate wascollected by filtration and dried under vacuum. The product weighed 19.8g (95.6% yield); m.p.=81.5°-82° C. Results of the elemental analysis andmain absorption peaks in the infrared spectrum are listed below.

Analytical: Elemental Analysis: Calculated: C=58.33, H=7.19, N=6.03,O=28.27; Found: C=58.40, H=7.08, N=6.19, O=28.3

Infrared Spectrum: (1) Urethane group: 3335 cm⁻¹ (NH), 1695 cm⁻¹ (COO),1540 cm⁻¹ (NH, CN), 1293 cm⁻¹ (CN, NH); (2) Ester group: 1770 cm⁻¹(COO), 1200 cm⁻¹ (C--O); (3) --CH₂ --O-- group: 740 cm⁻¹, 1460 cm⁻¹,1364 cm⁻¹ (CH₂ --O)

Solid State Polymerization:

The above compound turned blue within 24 hrs at room temperatureindicating thermal solid state polymerizability.

The above compound was crystallized from acetone and hexane and theresulting crystallized diacetylene was irradiated with Co⁶⁰ gamma raysat a dosage of 50 Mrads at room temperature. The resultingpolydiacetylene was a metallic (green-gold) polymer. The polymer wasextracted with isopropyl ether, and yielded polymer, melting point 137°C., in 95% conversion. The results of the elemental analysis and mainabsorption peaks in the infrared and Raman spectra are listed below.

Elemental Analysis: Calculated: C=58.33; H=7.19; N=6.03; O=28.27; Found:C=57.37; H=7.45; N=6.26; O=29.64

Infrared Spectrum: (1) urethane group: 3340 cm⁻¹ (N--H stretching), 1723cm⁻¹ and 1698 cm⁻¹ (COO), 1545 cm⁻¹ (NH,CN), 1200 cm⁻¹ (CN,NH); (2)ester group: 1753 (COO), 1200 cm⁻¹ (C--O--C)

Raman Spectrum: 2092 cm⁻¹ (C.tbd.C), 1465 cm⁻¹ (C.tbd.C)

Thermochromism:

The above-prepared metallic green-gold polymer turned a red (orange)color upon heating to 135° C. On cooling the solid to room temperature,the solid reverted to its metallic color.

The above-prepared polydiacetylene was molded into film (about 3 mlthick) at 150° C. The film was pliable and a dark red color. Uponheating, the film turned light pink at 135° C. and upon cooling itreverted to a dark red color.

The above polydiacetylene was incorporated into Halar by milling the twomaterials at 500° F. and then molding the resulting mass at the sametemperature. The resulting Halar film (containing 5% by weight of thepolydiacetylene) was red in color. The film turned orange upon heatingto 135° C. and reverted back to its original red color upon cooling toroom temperature.

EXAMPLE 4 Synthesis of 5,7-dodecadiyn-1,12-diolbis(n-butoxycarbonylmethylurethane), 4DBCMU Synthesis:

Following the general procedure of Example 1, 9.7 g (0.05 mole) of5,7-dodecadiyn-1,12-diol and 19.6 g (0.125 mole) of butylisocyanatoacetate, CH₃ (CH₂)₃ --O--CO--CH₂ --N═C═O, were reacted in thepresence of 0.5 g of di-t-butyl-tin-di-2-ethylhexoate, 1 ml oftriethylamine and 200 ml of tetrahydrofuran. The reaction was allowed toproceed for 2 hours and then the mixture was poured into 2000 ml ofhexane. The resulting precipitate was collected by filtration and driedunder vacuum. The product weighed 23.0 g (yield 90.5%) m.p.=73.5° to74.5° C. Results of the elemental analysis and main absorption peaks inthe infrared spectrum are listed below.

Analytical: Elemental Analysis: Calculated: C=61.40, H=7.87, N=5.51,O=25.19; Found: C=61.47, H=8.03, N=5.36, O=25.13

Infrared Spectrum: (1) Urethane group: 3335 cm⁻¹ (NH), 1696 cm⁻¹ (COO)1545 cm⁻¹ (NH, CN), 1292 cm⁻¹ (CN, NH); (2) Ester group: 1768 cm (COO),1203 cm (C--O); (3) --CH₂ --O--: 740 cm⁻¹, 1460 cm⁻¹, 1370 cm⁻¹ (CH₂--O)

Solid State Polymerization:

The above compound turned blue within 24 hrs. at room temperatureindicating thermal solid state polymerizability.

The above compound was crystallized from acetone/hexane and thenirradiated with Co⁶⁰ gamma rays at a dosage of 50 Mrads at roomtemperature. The resulting polydiacetylene was a metallic green-goldpolymer. Unreacted monomer was extracted with isopropyl ether, yieldinga polymer having a melting point of 136° C. The conversion of monomerinto polymer was 92.7%. The results of the elemental analysis and mainabsorption peaks in the infrared spectrum and Raman spectrum are listedbelow.

Elemental Analysis: Calculated: C=61.40; H=7.87; N=5.51; O=25.19; Found:C=55.68; H=7.29; N=4.80; O=27.21

Infrared Spectrum: (1) urethane group: 3340 cm⁻¹ (N--H stretching), 1723cm⁻¹ and 1693 cm⁻¹ (COO), 1545 cm⁻¹ (NH,CN), 1200 cm⁻¹ (CN,NH) (2) estergroup: 1750 (COO), 1200 cm⁻¹ (C--O--C)

Raman Spectrum: 2087 cm⁻¹ (C.tbd.C), 1461 cm⁻¹ (C═C)

Thermochromism:

It was found that partially polymerized 5,7-dodecadiyn-1,12-diolbis(n-butoxycarbonylmethylurethane) produced by solid statepolymerization at room temperature, was also thermochromic. The solidturned blue when stored at room temperature for one day, which wasevidence of solid state polymerizability. This solid retained its bluecolor in the temperature range from -180° C. to room temperature. Upongradual heating from room temperature to 73° C., (the melting point ofthe polimer) the partially polymerized diacetylene gradually turnedviolet, at about 40° C.

The fully polymerized polymer, prepared above by gamma irradiation,followed by monomer extraction, underwent a metallic green-gold to redcolor transition at 110° C. and a red to yellow color transition at 137°C. On cooling to room temperature, the solid reverted to dark red colorhaving a green-gold tint.

The irradiated and extracted polydiacetylene was molded into film (about3 mil thick) at 150° C. The resulting film was pliable and dark red incolor and upon heating at 110° C., the film turned light pink in color.Subsequent cooling produced a dark red color.

The irradiated and extracted polydiacetylene was incorporated into Halarfirst by milling the two materials at 500° F. and then molding theresulting mass at the same temperature. The resulting Halar film(containing 5% by weight of the polydiacetylene) was red in color. Thefilm turned light orange in color at 110° C. and reverted to a red coloron cooling to room temperature.

Coating of the Polydiacetylene:

The above polydiacetylene was found to be highly soluble in organicpolar solvents such as acetone, tetrahydrofuran and chloroform. Forexample, the polydiacetylene was dissolved in acetone (1 g, in 100 ml).Thin coatings of the polydiacetylene were obtained by dipping a cleanglass slide into the above-prepared solution and also by spreading thesolution on a polyethylene film and allowing the solvent to evaporate. Avery thin red-colored coating of the polydiacetylene was obtained. Thecoating turned orange at 115° C. and yellow at 135° C.

General Procedure (A) for Preparation of a Polydiacetylene Gel

A polydiacetylene, in a quantity of 0.1250 grams, was placed into a 50ml flask. To the flask was added 25.0 ml of a gel-forming liquid. Thecontents were stirred overnight. In the case where the gel-formingliquid was also a solvent for the polydiacetylene at room temperature, agel formed upon stirring below room temperature. In the case where thepolydiacetylene was only sparingly soluble in the gel-forming liquid, agel did not form until the mixture was subsequently heated to the colortransition temperature.

General Procedure (B) For Device Preparation

The thin capillary end of a 9" long disposable pipette was sealed withan oxygen/gas torch. The capillary portion of the pipette served as thecontainer for the device. Three tenths ml. of the formed gel orresulting mixture of polydiacetylene and gel-forming liquid wasintroduced into the wide end of the pipette, which was shaken to allowthe contents to settle, into the capillary portion of the pipette. Thewide end was then closed by means of sealing as above, or with a cork.

General Procedure (C) for Measuring the Dissolution

Temperature (T_(d)) of the Gel Composition

The dissolution temperature, designated as T_(d), was measured by meansof a paraffin oil bath comprised of five hundred ml of paraffin oil in a600 ml beaker. The bath was heated and stirred by means of a hotplate/stirrer. The sealed pipette, prepared above in Procedure B, wasplaced into the bath together with a calibrated mercury thermometer in aside-by-side fashion, both being tightly clamped. The temperature of thebath was increased until a color transition occurred. The colortransition temperature was recorded and the bath was allowed to cooluntil a temperature at which the original color of the gel wasregenerated, designated T_(s), the gelation temperature, which was alsorecorded.

EXAMPLE 5

Following the General Procedures of A,B and C, described above, 0.5 wt.percent gel compositions of poly 3DBCMU and poly 4DBCMU were preparedand tested. Poly 3DBCMU and poly 4DBCMU were prepared by polymerizingthe corresponding diacetylene diol alkoxycarbonylmethylurethane monomerby gamma-radiation and extracting out residual monomer from the polymerwith acetone in the case of poly 3DBCMU and isopropyl ether in the caseof poly 4DBCMU. The results, illustrating the effect of polymercomposition on the dissolution temperature, gelation temperature, andthe observed color transitions, are listed below in Table I.

                  TABLE I                                                         ______________________________________                                        Effect of Polymer Composition                                                 System:                                                                       Polydiacetylene - Varied (see table below for chemical names)                 Gel Forming Liquid - o-Dichlorobenzene                                        Concentration - 0.5% (wt.)                                                                     Transition Temperature                                                        (°C.) Range                                           Polydiace-                                                                              Color        T.sub.d   T.sub.s                                      tylene    Transition   Heating   Cooling                                      ______________________________________                                        Poly 3DBCMU                                                                             blue-yellow  105.0-105.4                                                                             91.5-90.6                                    Poly 4DBCMU                                                                             red-yellow   65.3-66.6 43.2-42.8                                    ______________________________________                                    

As is seen, for a gel comprised of poly 3DBCMU in o-dichlorobenzene, ablue-yellow color occurs when heating the gel to a temperature of105.0°-105.4° C., and the resulting yellow color persists until thetemperature is lowered to 90.6°-91.5° C., the gelation temperature,whereupon the gel is regenerated.

EXAMPLE 6

Following the General Procedures of A, B and C, described above, gelcompositions containing various weight percentages of poly 3DBCMU wereprepared and tested to determine the effect of concentration on theobserved transition properties. Poly 3DBCMU was prepared by the sameprocedure as Example 2. Results are tabulated below in Table II.

                  TABLE II                                                        ______________________________________                                        Effect of Polydiacetylene Concentration                                       System:                                                                       Polydiacetylene    Poly 3DBCMU                                                Gel-Forming Liquid o-Dichlorobenzene                                          Concentration      Varied (See Table below)                                   Color Transition   Blue-yellow                                                Polydiacetylene                                                                              Transition Temperature (°C.) Ranges                     Concentration  T.sub.d      T.sub.s                                           (% weiqht of gel)                                                                            Heating      Cooling                                           ______________________________________                                        0.1            102.8-103.3  88.2-84.4                                         0.5            105.0-105.4  91.5-90.6                                         1.0            105.2-105.6  91.2-90.5                                         ______________________________________                                    

EXAMPLE 7

Following the General Procedures of A, B and C, 6.5 weight percent gelcompositions of poly 4DBCMU, prepared as in Example 4, in variousgel-forming liquids, were prepared and tested to determine the effect ongel properties. The results are listed below in Table III.

                  TABLE III                                                       ______________________________________                                        Effect of Different Gel-Forming Liquids                                       System:                                                                       Polydiacetylene    Poly 4DBCMU                                                Gel-Forming Liquids                                                                              Varied (See Table below)                                   Concentration      0.5% (wt.)                                                 Color Transition   red-yellow                                                              Transition Temperature (°C.) Ranges                                      Heating      Cooling                                           Gel-Forming Liquid                                                                           T.sub.d      T.sub.s                                           ______________________________________                                        Ethyl acetate  58.0-59.0    34.5                                              Methyl ethyl ketone                                                                          49.0-49.5    19.0                                              o-Dichlorobenzene                                                                            65.3-66.6    43.2-42.8                                         ______________________________________                                    

EXAMPLE 8

Following the General Procedures of A, B and C, gel compositionscontaining 0.5 weight percent poly 3DBCMU, prepared as in Example 5, ina liquid mixture of two gel-forming liquids were prepared and tested todetermine the effect on gel transition properties. The results aretabulated below in Table IV.

                  TABLE IV                                                        ______________________________________                                        Variation in the Dissolution Temperature                                      By Use of Two Gel-Forming Liquids                                             System:                                                                              Polydiacetylene                                                                            Poly 3DBCMU                                                      Gel-Forming Liquids                                                                        Mixture of two solvents                                                       (See Table Below)                                                Concentration                                                                              0.5% (wt.)                                                       Color Transition                                                                           blue-yellow                                               Gel-Forming Liquids Transition Temperature                                    o-Dichloro-                                                                             Dimethyl-     (°C.) Ranges                                   benzene   Formamide     Heating   Cooling                                     (% Vol)   (% Vol)       T.sub.d   T.sub.s                                     ______________________________________                                        100       --            105.0-105.4                                                                             91.5-90.6                                    75       25            70.4-70.9   29-28.7                                   ______________________________________                                    

EXAMPLE 9

The procedure described in Example 8 was repeated except thatmethylethyl ketone replaced o-dichlorobenzene as a gel-forming liquid.The results are tabulated below in Table V.

                  TABLE V                                                         ______________________________________                                        Variation in the Dissolution Temperature                                      By Use of Two Gel-Forming Liquids                                             System:                                                                              Polydiacetylene                                                                            Poly 4DBCMU                                                      Gel-Forming Liquids                                                                        Mixture of two solvents                                                       (See Table below)                                                Concentration                                                                              0.5% (wt.)                                                       Color Transition                                                                           Red-yellow                                                Gel-Forming Liquids                                                           Methyl Ethyl                                                                             Dimethyl-     Transition Temperature                               Ketone     Formamide     Heating  Cooling                                     (% Vol)    (% Vol)       T.sub.d  T.sub.s                                     ______________________________________                                        100        --            49.0-49.5                                                                              19.0                                        *90        10            36.5-38.0                                                                              0                                           ______________________________________                                         *This composition is particularly suitable for detecting abnormally high      body temperatures.                                                       

The above-described gel compositions are useful in devices formonitoring and indicating predetermined temperatures wherein a physicalstate transition occurs at the predetermined temperature, resulting in acolor change, said color change persisting until the temperature issubsequently decreased below the predetermined temperature. The devicecontaining the gel composition is thus regenerated and ready for reuse.

We claim:
 1. A composition consisting essentially of (A) at least onepolydiacetylene selected from the group consisting of 1,4 additionpolymers of conjugated diacetylene monomers having the formulaR--C.tbd.C--C.tbd.C--R¹ wherein R and R¹ are urethane groupsindependently selected from(I):--(CH₂)_(n) --O--CONH--CH₂ --COOA, wheren is an integer of 1-10 and A is C₁ -C₁₀ linear or branched alkyl; andpolymers of diacetylene monomers having said formulaR--C.tbd.C--C.tbd.C--R¹ wherein R and R¹ are identical urethane groupsselected from: (II):--(CH₂)_(n) --O--CONHB wherein(a) n is 2 and B isethyl, n-butyl or m-chlorophenyl; or (b) n is 3 and B is methyl, ethyl,phenyl or m-tolyl; or (c) n is 4 and B is methyl, ethyl, 2-chloroethyl,o-chlorophenyl, p-chlorophenyl, n-butyl or m-methoxyphenyl; saidcomposition also consisting essentially of (B) a liquid capable offorming a gel with said polydiacetylene and of forming a solution ofsaid polydiacetylene upon elevation of the temperature of the gel to atleast the dissolution temperature, said gel containing about 0.001 to 50weight percent of said polydiacetylene, and said solution having adifferent color from that of said gel and being capable of reversiblyreforming the gel in its original color upon cooling to the gelationtemperature; said liquid being at least one member of the groupconsisting of linear or branched C₅ -C₁₀ paraffinic hydrocarbons, linearor branched C₁ -C₅ halogenated alkanes containing 1-4 halogen atoms, C₂-C₄ linear or cyclic alkyl sulfoxides, C₄ -C₆ cyclic sulfones, C₂ -C₇N,N-dialkylalkanoamides, C₆ -C₁₀ aromatic hydrocarbons, C₆ -C₁₀halogenated aromatic hydrocarbons containing 1 to 4 halogen atoms, C₄-C₆ linear or cyclic mono-or diethers, C₂ -C₄ alkanoic acid and ethylesters therof, C₃ -C₆ linear alkyl ketones and C₂ -C₄ halogenatedalkanoic acids containing 1 to 3 halogen atoms.
 2. The composition ofclaim 1 wherein the gelation temperature is at least about 10° C. lowerthan the dissolution temperature.
 3. The composition of claim 1 whereinsaid dissolution temperature is about minus 77° C. to plus 130° C. 4.The composition of claim 1 wherein said polydiacetylene is present inabout 0.1 to 50 weight percent of the gel.
 5. The composition of claim 1wherein said polydiacetylene is a polymer of a diacetylene monomer ofthe formula: R--C.tbd.C--C.tbd.C--R', wherein R and R' are independentlyselected from the formula:

    --(CH.sub.2).sub.n --O--CONH--CH.sub.2 --CO--OA

wherein n is an integer value of 1-10 and A is C₁ -C₁₀ linear orbranched alkyl.
 6. The composition of claim 5 wherein R and R' areidentical, n is 3 or 4, and A is ethyl or n-butyl.
 7. The composition ofclaim 1 wherein said polydiacetylene is a polymer of a diacetylenemonomer of the formula: R--C.tbd.C--C.tbd.C--R, wherein R is selectedfrom the group consisting of the formula:

    --(CH.sub.2).sub.n --O--CONH--B,

wherein (a) n is 2 and B is ethyl, n-butyl, m-chlorophenyl; (b) n is 3and B is methyl, ethyl, phenyl or m-tolyl; or (c) n is 4 and B ismethyl, ethyl, 2-chloroethyl, o-chlorophenyl, p-chlorophenyl, m-tolyl orm-methoxyphenyl.
 8. The composition of claim 1 wherein said gel-formingliquid is capable of dissolving at least about one-tenth of a gram ofsaid polydiacetylene in one hundred ml. of said liquid at thedissolution temperature.
 9. The composition of claim 1 wherein saidliquid is hexane, methylene chloride, chloroform, dimethyl sulfoxide,tetramethylene sulfone, dimethylformamide, dimethylacetamide, benzene,toluene, xylene, naphthalene, o-dichlorobenzene, trichlorobenzene,diethyl ether, tetrahydrofuran, dioxane, glyme, acetic acid, ethylacetate propionic acid, trichloroacetic acid, trifluoroacetic acid,acetone, methylethyl ketone, or mixtures thereof.
 10. The composition ofclaim 1 wherein said polydiacetylene is poly [4,6-decadiyn-1,10-diolbis(n-butoxy carbonylmethylurethane)] and the gel-forming liquid isxylene, o-dichlorobenzene, or acetic acid.
 11. The composition of claim1 wherein said polydiacetylene is poly [5,7-dodecadiyn-1,12-diolbis(n-butoxycarbonylmethylurethane)] and the gel-forming liquid isxylene, o-dichlorobenzene or methylethyl ketone.
 12. In a device forreversibly indicating when a predetermined temperature has been reachedor exceeded including a container, a temperature-indicating material,positioned inside of said container, capable of reversibly undergoing acolor change when a predetermined temperature has been reached orexceeded, and a means for observing said color change; the improvementwhich comprises providing a polymeric gel of claim 1 as thetemperature-indicating material wherein the color change, formed at thepredetermined temperature, persists until a temperature lower than thepredetermined temperature is reached thereby restoring the originalcolor and physical state of the gel.